title: The effect of retinal defocus on simple eye-hand and eye-foot reaction time in traumatic brain injury (TBI).
abstract: OBJECTIVE
  The purpose of the experiment was to assess the effect of retinal defocus on simple eye-hand (E-H) and eye-foot (E-F) reaction time (RT) in traumatic brain injury (TBI).
  
  
  METHODS
  Sixteen subjects with traumatic brain injury (five males and 11 females; aged 22-34 years) participated in the experiment. These were compared with 16 visually-normal, age/gender-match subjects. Retinal defocus was introduced optically (plano, +1, +2, +3, +4, +10D and +2D × 90) in the spectacle plane with binocular viewing. E-H and E-F RT were assessed binocularly using the RT-2S Simple Reaction Time Tester (Advanced Therapy Products, Glen Allen, VA). The test target colour and angular subtense simulated a conventional red/green traffic signal at 120 feet.
  
  
  RESULTS
  There was no significant effect (p > 0.05) of retinal defocus on either E-H or E-F RT in each population. There was a significant effect (p < 0.05) of TBI on both E-H and E-F RT as compared with the normative data, with it being longer and more variable in TBI. Each RT condition was longest in those with moderate TBI.
  
  
  CONCLUSIONS
  Both RTs were robust to retinal defocus, thus suggesting central nervous system insensitivity for this simple RT task. However, the increased RTs and related variability found in TBI, especially in moderate TBI, have potential safety implications (e.g. driving a car, ambulating).
authors.affiliation: Brain Injury Research Group, SUNY, State College of Optometry , New York, NY , USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Gould
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Ciuffreda
authors.forename: Naveen K
authors.initials: NK
authors.lastname: Yadav
authors.forename: Preethi
authors.initials: P
authors.lastname: Thiagarajan
authors.forename: Benjamin
authors.initials: B
authors.lastname: Arthur
mesh_terms: D000328:Adult; D001930:Brain Injuries / Q000503:physiopathology*; D002490:Central Nervous System / Q000503:physiopathology*; D004596:Electroretinography; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D011930:Reaction Time; D012160:Retina / Q000503:physiopathology*; D013997:Time Factors